[AS3]Need help with depth sorting in tile based game!

i have a few questions, which i need solutions to, and these i didnt find in tonypa’s tutorials! Oh and these are for as3!

1)How do i create a large map in parts, so that it dosent lag?
2)How do i sort depth of multiple instances at runtime ? I need something of the type of swapping depth based on y axis in as2! the closest function i could find is the swapChildren() function, but i dont know how to implement it in this scenario!